Automatic driller



Aug. 26, 1939 c, E, MULLER ETAL 3,463,252

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AUTOMATIC DRILLER Filed Sept. 19, 1966 '7 Sheets-Sheet 5 (War/@J f. /V/'///er' W/ ///0n7 Gar/eff INVENJURJ ATTORNEY Aug. 26, 1969 C. E, M|LLER ET AL UTOMAT I C DRILLER 7 Sheets-Sheet G Filed sept. 19, 196e l NVliN '1 UR! A TTOHNE y Aug. 26, 1969 c. E. MILLER ETAL AUTOMATIC DRILLER 7 Sheets-Sheet '7 Filed Sept. 19. 1966 ol-xE-bx;

United States Patent O 3,463,252 AUTOMATIC DRILLER Charles E. Miller and William R. Garrett, Midland, Tex.,

assignors to Smith Industries International, Inc., a corporation of California Filed Sept. 19, 1966, Ser. No. 580,392 Int. Cl. E21b 17/04; E21c 15/00 U.S. Cl. 175-27 24 Claims ABSTRACT F THE DISCLOSURE Conti-action and extension of a telescopic joint just above a down hole percussor and drill bit in a drill string generate signals to which responds mechanism for lowering drill string thereby to maintain constant the weight on down hole percussor. Signals may be air pressure changes, vibrations, or other types. On receipt of initiating signal the lowering mechanism may be operated for a predetermined distance or a predetermined time or so long as there is predetermined pressure rise or until a second predetermined signal to stop is received.

This invention relates to earth drilling and more particularly to apparatus for automatically lowering a drill string as the drill bit progresses down the earth bore. Although especially suited for use in drilling apparatus employing air or other gas as a 4medium to cool the bit and bring the cuttings to the surface, it may also be used in connection with other drilling apparatus, e.g. a system employing circulating mud to cool the bit and bring the cuttings to the surface. The apparatus preferably is constructed to operate in response to pressure changes in the drilling fluid, air, gas, water, oil, mud, or other, created as the bit advances in the hole. In particular the apparatus is designed to respond to pressure changes created by the extension and contraction of a telescopic joint incorporating a choke, which joint is placed in the drill string close below the neutral point. In the case of air or gas drilling the joint is placed just above or close to the down hole percussor used to drive the impact type drill bit. A telescopic joint of this type is disclosed in U.S. patent application Ser. No. 569,727, led Aug. 2, 1966, by William R. Garrett, entitled Telescopic Joint, now Patent No. 3,410,355 to which reference may be made for a detailed description thereof.

As disclosed in said Garrett application, the telescopic joint may comprise a lower inner and an upper outer tube splined together so as to transmit torque while allowing limited relative axial motion, cooperating stops being provided to limit the extent of contraction and extension. Sliding seal means between the tubes provides for fluid tight transmission of fluid through the joint. Near its upper end the outer tube carries a spider on which is mounted a stinger extending down into the inner tube. The stinger carries a plug at its lower end adapted to cooperate with a constriction in the inner tube. When the joint approaches full extension the plug enters the constriction to signal such position by causing an increase of presence in the drill string that is observable at the surface.

In the case of air as a drilling fluid the rise in pressure occurs because within the limits of its capacity the motor driven air compressor unit forming part of the drilling apparatus is regulated automatically to maintain a constant rate of flow of drilling uid. When the plug of the telescopic joint approaches the constriction thereof, there is created a choke which impedes iiow of drilling fluid. In order to maintain a constant rate of flow the pressure in the drill string above the choke must be increased.

3,463,252 Patented Aug'. 26, 1969 The regulator or governor on the compressor unit is se't to maintain constant speed, which corresponds to constant rate of ow, and this means that when the telescopic joint moves to choking position the motor of the cornpressor unit must supply more power. 'In this case of a gasoline engine driving the compressor, the 4governor opens the throttle to the engine; when the engine loads up the driller can hear it and will know it is time to lower the drill string to contract the `telescopic joint a prescribed amount, something less than the full range of travel of the joint.

In the foregoing manner drilling can proceed with the intermittent downward progress of the drill string keeping up with the fairly steady downward travel of the drill bit. At the same time, the downward force on the drill bit will remain substantially constant, consisting of the weight of the drill string below the telescopic joint plus the weight of the lower half of the telescopic joint plus the force of the drilling fluid acting to extend the telescopic joint. Maintenance of proper downward force or weight on the drill bit is very important in order that drilling proceed rapidly but with a minimum bit wear.

According to the present invention, control apparatus is provided responsive to pressure rise in the drilling tiuid to automatically lower the drill string, thereby relieving the driller of this job. Briefly, means is provided responsive to the drilling fluid pressure to control means for vertically positioning the drill string. In accordance with one embodiment of the invention, whenever there is a sufficient pressure rise the drill string vertical positioning means is actuated to lower the drill string a predetermined distance. In accordance with another embodiment of the invention whenever there is a sufficient pressure rise the drill string vertical positioning means is actuated to lower the drill string for a predetermined time. In a third embodiment of the invention the drill string vertical positioning means is actuated to lower the drill string whenever and for so long as there is a suicient pressure rise.

In a fourth embodiment of the invention the drill string vertical positioning means is lowered until the telescopic joint reaches a predetermined position of contraction at which the joint creates a further signal, e.g. a pressure drop to which the pressure responsive means at the surface is responsive to deactivate the vertical positioning means.

In accordance with a fifth embodiment of the invention instead of using a means at the surface responsive to pressure of the drilling uid to control the vertical positioning means, the surface means is a vibratory signal responsive means and the telescopic joint includes a vibratory signal generator which is actuated whenever the joint nears full extension. The surface means responds to the vibratory signal to actuate the vertical positioning means.

Generally speaking, the invention encompasses the use of any signal generating means responsive to the position of the telescopic joint in combination with a surface means responsive to such signal to activate the vertical positioning means, either until the signal ceases, or for a predetermined time thereafter, or until the pipe has been lowered a predetermined amount, or until a further signal is received from the telescopic joint, or in other predetermined manner. The signal may be an air pressure rise or fall, a sound signal, an electric, magnetic, electromagnetic signal, a mechanical vibration, or any other desired type of signal. Broadly the characteristie features of the invention are the generation of the signal in response to the relative positions of the parts of the telescopic joint and the reception of the signal at the surface and use thereof to vertically position the drill string. In this regard the term telescopic joint is to be considered in its broadest sense, namely, a lost motion connection between the upper and lower portions of a drill string.

It is to be noted that when air or other gas (eg. natural gas) is used as the drilling fluid there is normally an air storage chamber between the air compressor unit and the drill string. In addition, there may be several hundred or even thousands of feet of drill string between the telescopic choke or other pressure signaling means and the pressure responsive means at the surface. Depending on the depth of the hole there may be as much as a second or so time lag between the restriction of flow at the telescopic choke and an increase of pressure in the drilling Huid at the surface (upper part of the drill string) sutlicient to be readily distinguishable from minor pressure fluctuations due to operation of ancillary equipment powered from the same air source. During the interim the compressor continues to operate at the same speed but with gradually opening throttle while the storage tank and drill string fill up with air causing the pressure to rise. During this same period the drill bit continues to advance and the telescopic joint further contracts. With a drilling rate of l-O to 30 feet per hour the joint would contract only about 0.03 to 0.1 inch. The telescopic joint disclosed in the aforementioned Garrett application has a travel of about three inches from initial throttling to maximum throttling position plus an additional two inches of travel from maximum throttling position to the limit of contraction. Therefore, there is no dificulty with the joint reaching its limit of travel before the pressure builds up enough to operate the pressure responsive means at the surface.

After pressure of the drilling uid, e.g. air, has risen enough to initiate operation of the surface controls there will be a further time lag due to the time required for the controls to actuate the drill string positioning means. This time lag should also be kept short. At the maximum the time should be short enough so that the telescopic joint will not reach the limit of its extension before the drill string is lowered. At a drilling rate of 30 feet per hour and a five inch travel of the telescopic joint, this means that the controls must operate to start downward motion of the drill string within fifty seconds.

It is furthermore desirable that the surface controls act quickly enough so that the telescopic choke does not move to maximum throttling position, for the greater the throttling or choking the more the pressure of the drilling fluid must rise and the greater the load and strain on the motor-compressor unit. Ultimately, if the load reaches the capacity of the unit, either the throttle will be full open or the governor will not open the throttle further and the unit will slow down, thereby slowing down the percussor motor at the bottom of the hole. Assuming that a one-tenth inch extension of the telescopic joint is permissible after throttling sufficient to initiate actuation of the surface controls and prior to beginning of downward motion of the vertical positioning means, and assuming as before a 30 feet per hour drilling rate, a one second response time lag at the surface is the limit.

It is also desirable that the surface controls actuate the vertical positioning means for the drill string quickly in order to minimize the length of time the telescopic joint is in the throttling position, for during throttling the air velocity through the choke is high, tending to cause rapid erosion. Also the clearances are reduced during throttling so that foreign matter tends to collect in the choke to interfere with its operation.

The apparatus of the invention may be classified as of the intermittent type since the vertical positioning means is actuated only periodically. It would be possible to provide a continuously operating vertical positioning means for the drill string and control its rate of downward travel continuously as a function of the pressure in the drill string. Not only would this require reduction or elimination of pressure variations due to factors other than downward progress of the bit but also it would be necessary for the telescopic choke in the drill string and also the surface controls to operate at all times in a throttling condition. This would be particularly detrimental to the life of the surface controls because of the more rapid erosion caused by the high velocity air and the clogging ofthe controls with dirt particles. A11 intermittently actuating system is preferred since opportunity is given for operation with valves wide open to purge the system and the time of throttling and rapid wear is reduced. It is to be observed however that in the third embodiment of the invention the telescopic joint or subsurface part of the system may be operating in a throttling condition all or most of the time and the surface control, though intermittent, may be operating one or more times per second with the result that downward travel of the drill string is substantially continuous.

A further desirable feature of the invention is the provision of means by which the automatic surface control apparatus can be overridden with a manual control so that the driller can operate the vertical positioning means manually. This is desirable for at times other apparatus such as hoists, grinders, sprayers, or cleaners may divert enough air from the compressed air supply system to interfere with proper automatic operation, e.g. by so loading the system as to prevent pressure build up sufficient to actuate the surface controls.

For a detailed description of preferred embodiments of the invention reference will now be made to the accompanying drawings wherein:

FIGURES 1 and 2 together form a vertical section through the telescopic choke disclosed previously in the aforementioned Garrett application, that is assigned to the same assignee as the present invention;

FIGURES 3 and 4 are sections taken at planes 3 3 and 4-4 of FIGURE l;

- FIGURE 5 is a schematic drawing, partly in section, showing an air drill embodying the invention, the down hole signalling means or telescopic choke and the surface control means being shown only as boxes;

FIGURE 6 is a schematic view of a simple form of surface control means that could be used in the apparatus of FIGURE 5;

FIGURE 7 is a schematic view illustrating an improvement on the control means illustrated in FIGURE 6;

FIGURE 8 is a schematic view illustrating a further improvement on the control means illustrated in FIG- URES 6 and 7;

FIGURE 9 is an exploded sectional view of a valve used in the FIGURE 8 construction;

FIGURE 10 is a schematic view similar to the upper portion of FIGURE 5 and showing generally a further modied form of surface control means; and

FIGURE l1 is a schematic view showing details of the surface control means of FIGURE 10;

FIGURES l2 and 13 together form an elevation, partly in section, through a modified form of telescopic joint that may be used in conjunction with the invention;

FIGURE 14 is a section taken at 14--14 of FIG- URE 12;

FIGURE l5 is a section through part of a modified surface control means to be used in conjunction with the downhole signalling means of FIGURES 12-l4;

FIGURE 16 is a schematic view of other parts of the modified surface control means of which part is shown in FIGURE 15;

FIGURE 17 is a view similar to FIGURE 13 showing a modification incorporating a sonic signalling means; and

FIGURE 18 is a schematic view of a modified surface control means to be used in conjunction with the downhole signalling means of FIGURE 17.

Referring now to FIGURES 1 and 2 there is shown a telescopic joint including an outer tube and inner tube 11. The other tube includes an upper pipe 12, a lower pipe 13, and a nut 14, all screwed together. There are a plurality of semi-cylindrical grooves (see FIG- URE 3) inside pipe 15 terminating at their lower ends d6. Within grooves 15 are received cylindrical steel bars 17 bearing against the lower ends 16 of the grooves and retained against axial motion by the lower end 19 of pipe 12. When the threaded pin 20 of pipe 12 is screwed into threaded box 21 of pipe 13, the bars 17 are securely held against axial motion.

The inner portions of bars 17 are slidably received in longitudinal semi-cylindrical grooves 30 (see FIGURE 3) in the outer periphery of the inner tube -11. At the ends of grooves 30 there are holes 31, 32 extending radially into the inner tube. Holes 31, 32 are provided to facilitate machining. They also provide at surfaces 33, 34 against which the ends of bars 17 abut at the maximum contraction and extension of the joint.

Except for the grooves 30, the inner tube makes a fairly close sliding t with the inner surface of pipe 12, as shown at 40. Pipe 13, however, below shoulder 41 near the lower end of the bars 17, has a larger inner diameter than the outer diameter of tube 11, as shown at 42, leaving an annular space 43 therebetween. There is an enlargement or hub 44 on inner tube 11, below the lower ends of grooves 30. Hub 44 makes a fairly close sliding fit with the inner surface of pipe 13, thus providing guide means to keep the tubes concentric during contraction and extension of the telescopic joint. The guide means also takes some of the load When bending moment is applied to the joint.

One or more radial ports 50 in hub 44 connect with one or more longitudinal ports 51 which in turn cornmunicate at their upper ends with annulus 43. With this arrangement fluid leaking between tube 11 and pipe 12 at 40 will travel down through annulus 43 and ports 51, S0 back into inner tube 11, thereby flushing out grooves 30.

Seal means comprising oppositely facing annular packing cups 60, 61 are received in grooves 62, 63 formed in the outer periphery of hub 44, making a sliding seal between inner tube 11 and pipe 13 of the outer tube. This prevents `fluid in the casing annulus, the fluid returning the cuttings to the surface, from contacting the -bars I17 and grooves 30 forming the spline means.

Below hub 44 of the inner tube 11 is of smaller outer diameter than at 40 forming an elongated neck 70. Near the lower end of the neck is an enlarged diameter portion 71 forming a stop means. The lower end 72 of hub 44 also forms a stop means. A ring 73 is held between the lower end of threaded pin 74 on pipe 13 and the bottom of threaded box 75 of nut 14. The ring 73 is initially split in two halves, then assembled on neck 70 and the two halves welded together. Then nut 14 is screwed onto pipe 13, the ring 73 being held therebetween. Ring 73 forms stop means on the outer tube engageable with the stop means 71, 72 on the inner tube to limit the extension and contraction of the joint.

The distance between stop means 71 and 72 minus the thickness of ring 73 is less than the distance between the surfaces 33, 34 minus the length of bars 17. Ring 73 is so positioned relative to stop means 73, 74 as to normally prevent the bars 17 from contacting surfaces 33, 34. However, if nut 14 should accidentally become unscrewed from pipe 13, the bars 17 and surfaces 33, 34 would then be engageable to hold the joint together and prevent a fishing job.

Whenever it is desired to replace seal means 60, 61, it is only necessary to unscrew nut 14 from tube 13, thereby allowing the fuller extension of the joint permitted by bars 17 and surfaces 33, 34. This exposes the seal means below the lower end of the pipe 13 so that the seal means can be replaced.

Below stop means 71 the inner tube 11 is provided with a threaded box for connection to a percussor, drill collar or other lower part of the drill string.

Referring now particularly to FIGURES 1 .and 4, the pipe 12 has a portion 90 of reduced outer and inner diameter forming a socket 91. A stinger 92 has a spider 93 at its upper end received in socket 91 and suitably secured in place, e.g. by a press lit, shrink tit, cement, or other means. Ports 94 provide longitudinal fluid passages through the spider.

The lower end of the stinger carries a plug 97 of fusiform cross section. A constriction 98 near the upper end of tube 11 has an inner peripheral cylindrical surface 99 of slightly larger diameter than the outer peripheral cylindrical surface 100 of the plug. Guide tapers 101, 102 are formed at the upper and lower ends of constriction 98. IPlug `97 and constriction 98 form choke means presenting an increased resistance to duid ow through the telescopic joint when the joint is near to full extended position wherein plug 97 is inside constriction 98. The choke means does not, however, prevent uid ow; it merely requires an increase in pressure in the upper part of the drill string to maintain any given flow rate. This signals the operator that it is time to lower the drill string.

When the telescopic joint is fully extended the plug 97 moves up past and out of constriction 98 to enable maximum flow to be achieved, as may be desirable to clean the well, e.g. before lowering the drill string, after drilling the full extent permitted by extension of the telescopic joint. No signal means is needed to tell the operator how far to lower the drill string since the telescopic joint has a known travel between full extended and full contracted positions. The operator merely lowers the drill string a lesser distance.

The upper end of pipe 12 is provided with a fishing neck and .a threaded pin 111 for making connection with the drill pipe or other drill string members thereabove.

Referring now to FIGURE 5 there is shown an air drill 200 including a truck 201 disposed on the surface of the earth 202 adjacent an earth bore or well 203. A casing 204 extends part way the well to exclude near surface waters from the well. Extending from the surface through casing 204 down to adjacent the bottom of the well is a drill string 205. The drill string comprises a plurality of tubular drill pipe members known as drill rods or drill steels, screwed together end to end. In the lower part of the drill string is incorporated the subsurface signalling means to telescopi-c choke 206 described in detail in connection with FIGURES 1 4. Below the choke 206 is connected an air hammer 207 driving a chisel like percussion bit 208. Air is supplied to the air hammer through the drill string. Rotary drives means 209 adjacent the upper end of the drill string rotates the drill string slowly to change the position of the bit.

The air hammer will usually be immediately above the percussion bit. The telescopic joint will usually be immediately above the air hammer but if desired there may be one or more joints of drill steel between the hammer and telescopic joint. The hammer is known in the mining .and oil well drilling industry as a Down Hole percussor to distinguish it from arrangements in which the hammer is above ground and there is a long pipe or bar (anvil) extending down the hole from the hammer to the bit. The hammer is usually a free piston air motor in which the piston, reciprocating for example at several hundred to several thousand (c g. 1500) strokes per minute, functions as a hammer to strike an anvil connected to the bit. Usually the anvil and bit are integral because threaded connections will fail.

It is desirable to control the weight on the bit very closely in order to avoid rapid deterioration of the bit.

surface. The telescopic choke 206 is inserted above the hammer and whatever joints of drill steel collars, if any, are desired, and below the lower end of the drill pipe, so that none of the weight of the drill pipe is imposed on the bit, thereby automatically achieving the desired result.

Periodically when the joint approaches or reaches the limit of its extension as the bit drills deeper into the hole the operator may lower the drill string to contract the telescopic joint so as to allow the bit to continue its downward travel in the bottom of the hole. 'In accordance with the present invention the lowering of the drill string when the telescopic joint approaches or reaches the limit of its extension is accomplished automatically.

Referring still to FIGURE 5, on the truck is mounted a power source such as a gasoline engine 210 driving an air compressor 211. The compressed air, e.g. at pressure in the range of 50 to 300 p.s.i., is delivered from the compressor to storage tank 212. The tank may, for example, have a capacity of the order of several hundred gallons. A fluid conduit 213 connects through hose 214 from the storage tank to the top of the drill string 205 and the rotary drive means 209. A branch pipe 21S conducts air through surface control means 216 to pipe 217 leading to air motor 218. Motor 218 rotates lower sprocket wheel 219 over which passes one bend of continuous 220. The other bend of the cable passes around upper sprocket wheel 221. The sprocket wheels 219, 221 are rotatably mounted on tower 222 carried by the truck. The rotary drive means 209 in which the upper end of the drill string is suspended is slidably mounted at 223, 224 on tracks carried by the tower and is attached to cable 220. As the motor 218 drives the cable 220, the rotary drive means 209 is moved up or down raising or lowering the drill string. There is thus provided a vertical positioning means for the drill string.

The combination of the rotary drive means 209 and the drive motor 218 with associated sprocket wheels and chain is known as -a top head drive, to be distinguished from other conventional drilling arrangements which could be used with this invention such as the combination used in drilling oil wells comprising a rotary table and a hoist. The present invention is especially well suited for use with a top head drive.

Since the air supply for motor 218 passes through surface control means 216, the vertical position means for the drill string is under the control of surface control means 216. In perhaps its simplest form, as shown in FIGURE 6, control means 216 may comprise simply a normally closed spring loaded relief valve 230 disposed between air pipes 215, 217 and set by means of adjustment 231 to open at a pressure somewhat higher, e.g. 2 p.s.i., than the normal operating pressure in drill 'string 205. Whenever the telescopic choke 206 extends so far as to cause a pressure increase of 2 p.s.i., the relief valve 230 opens and actuates the vertical positioning means to lower the drill string.

An objection that may be made to the surface control means of FIGURE 6 is that most relief valves open rather gradually so that initially only a low volume of air would be fed to the sheave drive motor or top head feed 218, insufficient to operate the motor which may for example have a rating of l horsepower. To operate such a motor a large pressure increase, e.g. 8 to 12 p.s.i., might be required to open most relief valves suiciently. Such a large pressure increase would load the compressor unduly. Also, if the relief valve operates only after a large pressure rise, the slow response gives time for the telescopic choke to throttle down more which is also undesirable as previously explained. Therefore, a specially designed relief valve, e.g. a two-way snap acting valve, is required.

FIGURE 7 illustrates a modified surface control means that may be constructed with more conventional valving. In place of the simple spring loaded relief valve 230 of the FIGURE 6 construction, a pilot operated diaphragm relief valve 240 such as a Norgren A-1014B-04-A1 type valve manufactured by C. A. Norgren Co., 3400 S. Elati St., Englewood, Colo., may be employed. In connection with valve 240 is used a pressure regulator 241 such as a Norgren 11-002-019 pressure regulator. The regulator 241 is set by means of adjustment 242 to maintain a constant pressure slightly, e.g. 2 p.s.i., above the normal operating pressure of the drill string. The regulator 241, fed from pipe 215 through pipe 243 discharges through pipe 244 to the top of valve 240 and normally maintains the valve 240 closed. If pressure in the drill string rises 2 p.s.i. above normal, relief valve 240 opens quickly and fully, thereby causing prompt operation of the vertical positioning means to lower the drill string.

The FIGURE 7 construction illustrates a surface control means which will be operating on-ol at relative high frequency, e.g. once every second, and in conjunction with which the subsurface signal means or telescopic choke will be continuously maintained in a throttling position or close thereto. Operation of the vertical positioning means will be nearly continuous. A construction better suited for use in conjunction with a 12 inch stroke telescopic joint such as shown in FIGURES l-4 is shown in FIGURE 8.

Referring now to FIGURE 8 there is shown normally closed, time delay on closing, main valve 250 taking the place of valve 230 or 240 in the control means of FIGURE 6 or 7. Valve 250 may, for example, be a Norgren A-l0l4B-04-A1, 2Way In Line 0-60 second TDR (Delayed on release) Normally Closed Air Operated 1/2 Valve.

As shown in FIGURE 9, valve 250 includes a hollow body 251 having inlet port 252 and outlet port 253 separated iby partition 254. In partition 254 is a llow passage 255 over which is normally positioned valve disc 256. The valve disc is urged against its seat 257, formed 'by the periphery of ow passage 255, by a helical spring 258. Valve disc 256 is connected by valve stem 259 to actuating piston 260. Piston 260 receives air through passage 261 of the time delay head 262. Over the top of time delay head 262 is a cover 266 seated and slightly spaced from head 262 by a gasket 267. A port 268 in cover 266 is adapted to connect to a source of actuating air.

Flow of air to passage 261 is controlled by spool valve 263 which in turn is connected to passage 264 through check valve 265 to port 268. Spool valve 263 is shown in position to block flow of air to passage 261 so that valve 250 is closed: Air from the upstream inlet 252 is conducted through ports 270 and 271 to the left side of the core of the spool valve, always urging it to the left. However when actuating air is applied to port 268, some of the air after going through check valve 265 enters passage 272 leading to air chamber 273. The latter is connected by port 274 to the right end of the core of the spool valve. Since this end is larger than the other, the core moves to the left, opening port 264 and admitting air to actuating piston 260, thereby opening the valve 250. When the air supply port 268 is cut off, valve 250 stays open until the pressure in chamber 273 drops. Chamber 273 is vented to port 268 through a needle valve controlled by adjustment screw 269 and through passage 274. When the core of the spool valve moves to the right, not only is port 264 cut oif but port 276 is opened venting the space above actuating piston 260 to insure the opening of valve 250. Since this is a commercially available valve, further detail of description is unnecessary. Furthermore, it is to "be understood that other known time delay on reclosing valves may lbe used in place of the one described.

Referring again to FIGURE 8, to the port 268 in valve 250 is connected pipe 280 which in turn is connected to the outlet of a pilot operated diaphragm relief valve 281 which may in all respects be the same as valve 240 of the FIGURE 7 construction. Valve 281 receives air through pipe 282, solenoid valve 283, pipe 284, handgate valve 285, and pipe 286 from pipe 215. As in the FIGURE 7 construction, valve 281 is connected by a pipe 290 to a pressure regulator 291 which receives air through pipe 292 and pipe 282. Therefore, when solenoid valve 283 is closed both regulator 291 and pilot actuated valve 281 are shut ofI" from air with the result that main valve 250 is closed This is the condition when the threeway switch 300 is in the olf position.

When switch 300 is moved to the automatic position, current from battery 301 energizes the solenoid of valve 283 and opens the valve. If the pressure in line 215 rises above the normal operating pressure of the air in the drill string to the pressure at which regulator 291 is set, e.g., 2 p.s.i. above said normal operating pressure, the relief valve 281 opens quickly and fully and causes main valve 250 to open. 'This is quite similar to the operation of the control means of the FIGURE 7 construction. However, upon drop in pressure in pipe 215, the main valve 250 remains open for whatever period to 60 seconds) it is set. The vertical positioning means continues to lower the drill string. The time of reclosing of valve 250 is set so that the drill string will be lowered enough to vbring the telescopic joint to a position of near to full contraction well away from the throttling position thereof. Ultimately valve 250 recloses and the drive motor 218 of the vertical positioning means stops. The time ldelay (t) in the closing of valve 250 is related to the velocity (v) of down travel of the vertical positioning means and the distance (d) when it is desired to lower the drill string by the usual law and in an actual case may be of the order of several seconds more or less, e.g. 3 seconds.

In case the normal pressure in pipe 215 should drop so as to render the automatic control system relatively unresponsive or if for any other reason it is desired to operate the vertical positioning means manually, switch 300 may be moved to the manual position. In that position lsolenoid valve 283 is closed but another solenoid valve 310 is opened. Valve 310 is connected by pipes 311, 312 between pipes 284 and 280 so that when valve 310 is open air is supplied to main valve 250 to open same and actuate the vertical positioning means to lower the drill string. When it is desired to discontinue lowering the drill string, switch 300 is moved to the off position and after the predetermined time delay valve 350 will close. Because of this time lag it will be understood that the driller desiring to operate the system manually would move lswitch 300 to the manual position only long enough to open valve 310 and would immediately thereafter move switch 300 to the olf position, thus allowing the preset time delay of reclosing of main valve 250 to determine the time of down travel of the vertical positioning means.

In order to relieve the pressure in pipe 280 upon closing of overriding solenoid valve 310, a vent is provided through the valve stem to exhaust at 320. This exhaust is open only to the downstream side of valve 310 when the valve is closed. This vent also functions to relieve the pressure in pipe 280 upon closing of valve 281 during automatic operation of the system.

If it is desired to shut olf both the automatic and manual (semi-automatic) controls and utilize the regular pure manual control provided on the drill, master gate valve 285 may be closed. Under such circumstances it may also be desirable to completely isolate the subject control system and to that end downstream gate valve 321 may be closed. Whenever it is desired to blow out any water or other foreign matter collected in the air pipes, exhaust gate valve 322 may be opened.

The switch 300 may be moved about to any place convenient to the driller. -If electrical remote control is considered undesirable for any reason, a three-way air valve may be used controlling air to air actuated valves substituted for solenoid valves 283, 310.

Although air operated valves have been shown in the control system, electric operated pressure sensing valves and operators can be substituted throughout the system. Also, the functions of the several physically separate components of the system can be combined into fewer components if desired. The disclosed consrtuction, however, does have the advantage of being capable of assembly out of presently commercially available coniponents.

Referring now to FIGURES 10 and ll there is shown another form the control means 216 can take. A pilot controlled relief valve 340, which may be the same as valve 240 of the FIGURE 7 construction, is placed between pipes 215 and 217. A pilot valve 341 is connected by pipe 342 to air supply pipe 215 and the outlet of valve 341 is connected through pipe 343 to relief valve 340. Whenever the pressure in pipe 215 rises a preset amount, pilot valve 341 opens and this in turn opens relief valve 340. Howver, when the pressure in pipe 215 drops due to actuation of the vertical positioning means by the opening of valve 340, pilot valve 341 is prevented from reclosing by mechanical locking means including a circular cam 344 and a cam follower 345. The cam follower is connected to the closure disc 346 of valve 341 through seal 347. The follower 345 holds the valve open except when the cam is positioned so that its notch 348 will receive follower 345 and allow valve spring 349 to close the valve.

Cam 344 is releasa'bly connected by retractable pin 350 to one end of spool 351 on which are wound several turns of a wire 352. One end of wire 352 (see especially FIGURE l0) passes over sheave 219 and is anchored to the rotary drive means 209. The other end of wire 352 passes over a special sheave 353 rotatably mounted on tower 222 and is connected at its end to a weight 354 which either hangs freely as shown or is vertically slidable in guide means provided on the tower. The wire 352 Iand its associated sheaves and spool 251 and pin 350 thus provide drive means releasably interconnecting the drill string and cam 344 to cause the cam to rotate in proportion to the vertical travel of the drill string. This drive means is constructed so that one revolution of the cam corresponds to the desired downward travel of the drill string after the telescopic choke has signaled that it is time to lower the drill string. Whenever the pressure in pipe 215 rises to the value at which relief valve 341 is set, e.g. one or two percent above normal pressure in the drill string, valve 341 opens causing valve 340 to open to actuate motor 218 of the vertical positioning means. The latter then lowers the `drill string and cam 344 rotates, the follower 345 being elevated out of notch 348 by the opening of valve 341. The valves 341 and 340 stay open and the motor 218 continues to operate until the cam has made one revolution positioning notch 348 under follower 345 and allowing valve 341 to close.

It will be readily apparent that valve 341 could itself be pilot operated the same as valve 240 is pilot operated by regulator 241 in the FIGURE 7 construction.

Instead of providing surface control means activating the vertical positioning means to lower the drill string a predetermined distance as shown in FIGURES 10 and 11, the surface means can be constructed to continue the actuation of the vertical positioning means until a further signal is received from the down hole signalling means. For example the telescopic joint may include a vent opened when the joint is near full extended to signal the surface by a drop in pressure and a choke that is actuated to raise the pressure when the joint is near full contraction. Such joint is shown in FIGURES l2, 13, and 14 and a suitable surface control means cooperable therewith is shown in FIGURE 15.

Referring now to FIGURES 12-14, the telescopic joint there shown includes an upper outer tubular member 400 having a threaded box 401 at its upper end adapted for connection in a drill string. The joint further includes a lower inner tubular member 402 axially slidably disposed in member 400. As shown best in FIGURE 14, a bar 403 is mounted in holes 404, 405 in member 400, being welded in place. The bar 403 extends through slots 406, 407 in member 402, thereby providing means to transmit torque between the outer member 400 and inner member 402 while allowing relative axial motion therebetween. Bar 403 is of reduced transverse dimension at its mid-portion 408 to provide a maximum fluid passage through the joint.

Above bar 403 there is a choke means including a tapered throat 410 formed at the upper end of inner member 402, and a tapered plug 411 carried at the lower end of Stringer 412. Stinger 412 is mounted in a spider 413 secured in outer member 400, there being fluid passages between the webs of the spider. When the joint approaches full contraction, as limited by bar 403 engaging the lower ends of slots 406, 407, the plug 411 approaches seat 410 closely enough to provide a flow construction but not enough to block fluid flow.

Referring now particularly to FIGURE 13 below bar 403 the outer member carries a liner sleeve 415 pressed or shring fitted or otherwise secured in enlarged bore 416 in the lower end thereof. Sleeve 415 cooperates with split metal (steel) seal ring 417 snapped into groove 418 on the enlarged diameter position 419 at the lower end of inner member 402. The telescopic joint is thus sealed against escape of air or other drilling fluid passing therethrough, but only so long as seal 417 is above longitudinal slots 420 in the lower end of sleeve 415.

When the joint approaches full extension, as limited by engagement of bar 403 with the upper ends of slots 406, 407, the ring 417 passes below the upper ends of slots 420 allowing fluid inside the joint to escape. The escaping fluid, e.g. air, will pass through the clearance annulus between the inner member 402 and outer member 407 beginning at the upper end of the inner member adjacent throat 410 and thence down past liner sleeve 415, through slots 420, and the annular space 421 between enlarged portion 419 of the inner member and enlarged bore 416 in the outer member, and linally emerge through the clearance between guide hub 422 at the lower end of the inner member and bore 416 in the outer member.

Circumferentially spaced slots 423 extend longitudinally from adjacent annular space 421 to below the lower end 424 of the outer member when the joint is in near full extended position. Slots 423 thus provide fluid by pass means over the surface of hub 422. Hub 422 can therefore be dirnensioned to make a close sliding t with the bore 416 as is desirable to enable the joint to transmit bending moments and to prevent wobble.

Inner member 402 has a further enlarged portion 430 below hub 422. Wrench receiving ats 431, 432 are formed in portion 430. Similar flats 433, 434 are formed at the upper end of the inner member as shown in FIG- URE l2.

The telescopic joint shown in FIGURES 12-14 is similar to that shown in FIGURES 1-4 but differs in that it provides a fluid exhaust rather than a ow constriction when the joint approaches full extension. It thus signals the surface that the joint is near full extension by causing a drop rather than a rise in uid pressure. When the driller notes the drop in pressure he can activate the vertical positioning means to lower the drill string. He can either lower the drill string a predetermined amount as in the use of the joint of FIGURES 1 4 or he can rely on the rise in pressure due to the oor construction as the joint approaches full contraction as a signal that the drill string has been lowered suliiciently. According to the present invention surface con'trol means responsive to the pressure signals received from the joint are provided 12 to automatically activate the vertical positioning means. This is shown in FIGURES 15 and 16 to which reference will now be made.

Referring also to FIGURE 5, pipe 450 of the FIGURE 15 surface control means is to be connected to pipe 215 which is connected to pipe 213 coming from the air storage tank 212 shown in FIGURE 5. It will be recalled that pipe 213 supplies air (or other drilling fluid) to drill string 205. Therefore the pressure in pipes 213 and 215 and in pipe 450 connected thereto is subject to the pressure variations caused by the telescopic joint of FIGURES 12-14 which is to be used as the joint 206 shown in FIGURE 5.

When the pressure in pipe 450 drops, e.g. a few p.s.i., spring 451 overcomes the pressure acting on piston 452 and the lat'ter moves to the left. As piston 452 moves to the left, piston -rod 453 pushes stem 454 of spool valve 455 to the left. This opens port 456 to atmosphere and communicative port 457 with the interior of the body 457 of the spool valve. As a result, lluid from pipe 458 passes through spool valve 455 to the left side of piston 459 forcing piston rod 460 to the right. Rod 460 is connected to stem 461 (FIGURE 16) of gate valve 462, which is thereby opened. When valve 462 opens, air feeding from pipe 215 through pipe 463 is supplied to valve 464 which is similar to valve 340 shown in FIGURE l1. When valve 464 opens, air is fed through pipe 465 to top head drive motor 218 (FIGURE 5). This lowers the drill string 205.

When the drill string lowers enough to close the vent passage means of the telescopic joint, the line pressure of the drilling fluid returns to normal and piston 452 (FIG- URE 15) moves to the right, overcoming compression spring 451. Stem 454 of spool valve 455 remains in the same position however and the vertical positioning means continues to lower the drill string.

When the drill string is lowered enough so that the telescopic joint approaches full contraction, the flow constriction means of the joint becomes ac'tive and causes a rise in pressure of the drilling lluid. When the line `pressure thus rises, e.g. a few p.s.i., the pressure at the left of piston 470, fed through pipe 470il overcomes compression spring 471 and moves piston rod 472 to the right. This moves spool valve stem 454 to the right, as shown, opening port 457 to atmosphere and communicating port 456 with line pressure. Piston 459 is thus caused to move to the left, carrying with it stem 461 of gate valve 467, thereby closing Valve 462. When pilot valve 462 closes, valve 464 closes and deactivates the vertical positioning means.

The operating pressures for pistons 452 and 470 can be adjusted by varying the prestress in springs 451 and 471. This can be done by varying the position of screws 480 and 481 screwed into the ends of cylinders 482, 483 respectively.

Referring now to FIGURE 17 there is shown a modication of fthe lower part of the telescopic joint of FIG- URES 12-14. In this modification a sharp lipped bridge 500 is incorporated in one of the slots 421 leaving a narrow flow passage 501 between the lip of the bridge and bore 416. Just below bridge 500 there is a vent port 502 extending through outer member 400. When the join't approaches full extension and ring 417 passes below the upper ends of slots 421, the air escaping past bridge 500 will create a sonic vibration, c g. a whistle, whose pitch will depend on the length of the resonating air columns available, e.g. in slo'ts 423. Such sonic vibration means can be provided in each of the slots 421 if desired. Except as noted, the remainder of the lower part of the telescopic joint shown in FIGURE 17 is the same as that shown in FIGURE 13. The upper part of the telescopic joint will be the same as that shown in FIGURE 12, except that the ow construction means including stinger 412 and plug 411 may be omitted.

With a telescopic joint as described with reference to FIGURE 17 incorporated in the drill string at 206 (FIG- URE whenever the joint approaches full extension a sonic vibration is created which is detectable at the surface and can be used to actuate the vertical positioning means. FIGURE 18 shows a suitable surface control means to be used at 216 (FIGURE 5) in conjunction with the telescopic joint of FIGURE 17.

Referring to FIGURE 18, a michophone 520 placed in position to pick up acoustic vibrations in the drill string or drilling uid, eg. near or in contact with pipe 215, generates an electric signal which is amplified by electric amplifier 521. The signal passes through filter S22 which is tuned to pass only the band of frequencies of vibrations generated by the sonic signal of the telescopic joint, thereby to eliminate spurious signals. After passing through lter 522 the signal is transmitted to power amplier 523 which is connected to relay 524. When the relay is actuated by the signal to close switch 525, battery 526 supplies current to open solenoid pilot valve 527. When valve 527 opens, air is fed through pipes 528, 529, to time delay on closing valve 530. The latter valve is similar to that shown in FIGUR-E 9. Valve 530 is thus opened and activates the vertical positioning means by supplying air through pipe 217 to motor 218 of the top head drive (FIGURE 5).

When the vertical positioning means has been actuated long enough to contract the telescopic joint to the point where its vent means is closed, the sonic signal is discontinued. However the vertical positioning means continues to operate during the time which valve 530 requires for closing. In this respect the operation is similar to that of the FIGURE 8 construction.

From the foregoing description it is to be understood that the invention includes down hole signalling means and surface control means responsive to signals from the down hole signalling means to control the vertical positioning means for the drill string. In one aspect the invention is characterized by signalling means operating by variations in the pressure of the drilling fluid, regardless of how such pressure variations are generated. In another aspect, the invention is characterized by signalling means dependent upon the relative positions of the parts of a telescopic joint, regardless of the nature of the signals generated, e.g. pressure rise, pressure fall, sonic vibrations, electric, magnetic, electromagnetic, or other form of signal. Furthermore, the features and the variations of the elements of each of the several constructions may be employed with any and all of the constructions described. For example, the override and remote control means of the FIGURE 8 construction could readily be added to the construction of FIGURES 10 and 11 or to the constructions of FIGURES 6, 7, 16, or 18. Likewise, electrically powered pressure sensitive valves and operators can be used with any of the several constructions in place of the air powered equipment shown in the drawings.

It is also to be understood that the drive motor 218 could easily be a hydraulic or an electric motor and that the main air control valves 215, 240, 250, 340 of the several constructions of surface control means illustrated could in such case be replaced by hydraulic control valves or electric switches.

Finally, it is to be recalled that although the invention is especially adapted for use in air drilling, similar subsurface and surface controls can be used in drilling with other fluids such as gas, water, oil or mud.

In conclusion, although preferred embodiments of the invention have been shown and described, many modifications thereof can be made by one skilled in the art Without departing from the spirit of the invention.

We claim:

1. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a drill string including an upper portion and a lower portion,

a drill bit connected to the lower portion of said drill string,

positioning means at the upper portion of said drill string for raising and lowering same,

down hole signalling means responsive to the position of the drill bit, and

surface control means responsive to signals from the down hole positioning means to control said positioning means,

said signalling means signalling by generation of oscillating vibrations, and

said surface control means including means responsive to oscillating vibratory signals transmitted from said signalling means.

2. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a tubular string including an upper portion and lower portion,

a drill bit connected to the lower portion of said drill string,

positioning means at the upper portion of said drill string for raising and lowering same,

down hole signalling means responsive to the position of the drill bit,

surface control means responsive to signals from the down hole positioning means to control said positioning means, and

means to cause ow of fluid under pressure through said drill string,

said signalling means signalling said surface control means by acting on said pressure fluid,

said signalling means including a -whistle and said surface control means including a microphone.

3. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a tubular string including an upper portion and a lower portion,

a drill bit connected to the lower portion of said drill string,

positioning means at the upper portion of said drill string for raising and lowering same, down hole signalling means responsive to the position ofthe drill bit,

surface control means responsive to signals from the down hole positioning means to control said positioning means, and

means to cause flow of fluid under pressure through said drill string,

said signalling means signalling said surface control means by acting on said pressure iiuid.

said signalling means acting on said pressure fluid to cause a change of pressure therein, and

said surface control means including means responsive to change of pressure of said fluid.

4. Combination of claim 3 wherein said signalling means causes a rise in pressure of said fluid to signal said surface control means to lower the drill string.

5. Combination of claim 3 wherein said signalling means causes a fall in pressure of said uid to signal and surface control means to lower the drill string.

6. Combination according to claim 5 wherein said signalling means causes a rise in pressure of said fluid to signal said control means to discontinue lowering of said drill string.

7. Combination of claim 3 wherein said surface control means includes means responsive to receipt of a pressure change signal from said signalling means to cause lowering of said drill string.

8. Combination of claim 7 wherein said surface control means further includes means responsive to the passage of a predetermined time after receipt of said pressure change signal to cause discontinuance of lowering of said drill string.

k9. Combination according to claim 7 wherein said surface control means includes means responsive to lowering of the drill string a predetermined distance to cause discontinuance of the lowering of the drill string.

10. Combination according to claim 7 wherein said surface control means includes a uid conduit communicating at one end with said pressure fluid adjacent the upper portion of said drill string and at another end with said vertical positioning means, and

valve means in said fluid conduit responsive to pressure of said fluid to open and close.

11. Combination according to claim 10 wherein said valve means includes a pilot controlled valve having a through flow passage connected in said conduit and a control chamber connected through a line to said conduit upstream from said pilot controlled valve, and

a pilot valve means in said line responsive to pressure in said line upstream from said pilot valve means to open and close said pilot valve means.

12. Combination according to claim 11 wherein said pilot controlled valve includes time delay means to delay return to normal position until a predetermined time after actuation by said pilot valve means.

13. Combination ot claim 12 wherein said pilot valve means includes cam means driven in response -to the motion of said drill string to prevent return of said pilot valve means to normal following actuation thereof until said drill string has been lowered a predetermined amount.

14. Combination according to claim 12 wherein said pilot valve means includes an auxiliary pilot controlled valve having a How passage connected in said line and a control chamber connected to said line by a pipe, and

a pilot valve in said pipe responsive to pressure in said pipe upstream from said pilot valve to open and close said pilot valve.

1S. Combination according to claim 14 including a remote controlled solenoid valve means controlling iuid flow to said pipe and said line to deactivate said control means when desired,

a bypass connecting said control chamber of the lirst said pilot controlled valve to said iluid conduit independently of said line, and

a second remote controlled solenoid valve means controlling ow of uid through said bypass to actuate said control means in response to the position of said second remote controlled solenoid valve means.

16. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a drill string including an upper portion and a lower portion,

a drill bit connected to the lower portion of said drill string,

positioning means at the upper portion of said drill string for raising and lowering same,

down hole signalling means responsive to the position of the drill bit, and

surface control means responsive to signals from the down hole positioning means to control said positioning means,

said drill string including a telescopic joint,

said joint having a `first part connected to said upper portion of the drill string and a second part connected to said lower portion of the drill string to which the drill bit is connected,

said signalling means responding to predetermined positioning of said second part relative to said iirst part to signal to the surface control means to actuate the positioning means to lower the upper portion of the drill string,

said surface control means including means responsive to the passage of a predetermined time after initiation of the actuation of said positioning means to cause discontinuance of the operation of said positioning means. 17. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a drill string including an upper portion and a lower portion, a drill bit connected to the lower portion of said drill string, positioning means at the upper portion of said drill string for raising and lowering same, down hole signalling means responsive to the position of the drill bit, surface control means responsive to signals from the down hole positioning means to control said positioning means, said drill string including a telescopic joint, said joint having a first part connected to said upper portion of the drill string and a second part connected to said lower portion of the drill string to which the drill bit is connected, said signalling means responding to predetermined positioning of said second part relative to said tirst part to signal to the surface control means to actuate the positioning means to lower the upper portion of the drill string, said surface control means including means responsive to the lowering of said upper portion of the drill string a predetermined distance after initiation of the lowering of the upper portion of the drill string to cause discontinuance ofthe operation of said positioning means. 18. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a drill string including an upper portion and a lower portion, a drill bit connected to the lower portion of said drill string, positioning means at the upper portion of said drill string for raising and lowering same, down hole signalling means responsive to the position of the drill bit, surface control means responsive to signals from the down hole positioning means to control said positioning means, said drill string including a telescopic joint, said joint having a rst part connected to said upper portion of the drill string and a second part connected to said lower portion of the drill string to which the drill bit is connected, said signalling means responding to predetermined positioning of said second part relative to said tirst part to signal to the surface control means to actuate the positioning means to lower the upper portion of the drill string, said signalling means responding in a second predetermined position of the second part of the telescopic joint relative to the iirst part to signal to the surface control means to discontinue actuation of the positioning means. 19. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a drill string including an upper portion and a lower portion, a drill bit connected to the lower portion of said drill string, positioning means at the upper portion of said drill string for raising and lowering same, down hole signalling means responsive to the position of the drill bit, surface control means responsive to signals from the down hole positioning means to control said positioning means, said drill string including a telescopic joint, said joint having a first part connected to said upper portion of the drill string and a second part connected to said lower portion of the drill string to which the drill bit is connected,

said signalling means responding to predetermined positioning of said second part relative to said first part to signal to the surface control means to actuate the positioning means to lower the upper portion of the drill string,

said uid driving means including regulator means tending to maintain a constant rate of ow of fluid down through said upper part of the drill string, and

said signalling means including ow resistance varying means to vary the resistance to fluid ow downstream from the upper portion of said drill string.

20. Combination of claim 19 wherein said flow resistance varying means comprises flow constriction means in said telescopic joint to restrict flow when said second part of the telescopic joint is in said predetermined position relative to said first part of the telescopic joint.

21. Combination of claim -19 wherein said flow resistance varying means comprises vent means to vent iluid from said telescopic joint when said second part of the telescopic joint is in said predetermined position relative to said rst part of the telescopic joint.

22. Combination according to claim 19 wherein said signalling means responds in a second predetermined position of the second part of the telescopic joint relative to the first part to signal to the surface control means to discontinue actuation of the positioning means, and

said flow resistance varying means comprises vent means to vent uid from said telescopic joint when said second part of the telescopic joint is in the first said predetermined position relative to said first part of the telescopic joint and How constriction means in said telescopic joint to restrict tlow when said second part of the telescopic joint is in said second predetermined position relative to said irst part of the telescopic joint.

23. An automatic drilling apparatus for making a hole in the earth, said apparatus comprising a tubular drill string including an upper portion and a lower portion,

a drill bit connected to the lower portion of said drill string,

CAD

positioning means at the upper portion of said drill string for raising and lowering same,

down hole signalling means responsive to the position of the drill bit,

surface control means responsive to signals from the down hole positioning means to control said positioning means,

said drill string including a telescopic joint,

said joint having a tirst part connected to said upper portion of the drill string and a second part connected to said lower portion of the drill string to which the drill bit is connected,

said signalling means responding to predetermined positioning of said second part relative to said rst part to signal to the surface control means to actuate the positioning means to lower the upper portion of the drill string,

fluid driving means to transfer fluid under pressure through said drill string,

said signalling means signalling said surface control means by acting on said pressure fluid, and

down hole percussor means in said drill string between said drill bit and telescopic joint,

said predetermined position of said second part of the telescopic joint relative to said rst part corresponding to near full extension of said joint.

24. lCombination according to claim 23 wherein said vertical positioning means forms par-t of a top head drive for said drill string.

References Cited UNITED STATES PATENTS 1,891,062 12/1932 Sager 175-26 1,891,329 12/1932 Le Compte et al. 175-317 X 3,039,543 6/1962 Loocke 175-26 3,223,183 12/1965 Varney 175-27 STEPHEN J. NOVOSAD, Primary Examiner RICHARD E. FAVREAU, Assistant Examiner U.S. Cl. XR.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTIGN Patent No. 3,463,252 August 26, 1969 Charles E. Miller et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line Z7, before "220" insert cable Column 14, lines l0, 28 and 47, Column 1S, line 6l, Column 16, lines 13, 43 and 71, and Column 18, lines l and 6, "positioning", first occurrence, each occurrence, should read signalling Column 14, lines 19 and 38, after "tubular", each occurrence, insert drill line 61, "and" should read said Column l5, line 9, cancel "vertical". Column 17, line 7, "said" should read and line 9, cancel "and". Column 18, line 28 cancel "vertical".

Signed and sealed this 29th day of June 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

